DOCSLIB.ORG

Industrial Process Industrial Process

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Industrial Process Industrial Process INDUSTRIAL PROCESS INDUSTRIAL PROCESS SESSION 1 GENERAL PROCESS INDUSTRIAL PROCESS Industrial processes are procedures involving chemical, physical, electrical or mechanical steps to aid in the manufacture of an item or items, usually carried out on a very large scale. Industrial processes are the key components of heavy industry. Liquid nitrogen Liquefaction of gases is physical conversion of a gas into a liquid state (condensation). 1 Details 2 History 3 Linde's Process 4 Claude's Process 5 See also 6 External links Details The processes are used for scientific, industrial and commercial purposes. Many gases can be put into a liquid state at normal atmospheric pressure by simple cooling; a few, such as carbon dioxide, require pressurization as well. Liquefaction is used for analyzing the fundamental properties of gas molecules (intermolecular forces), for storage of gases, for example: LPG, and in refrigeration and air conditioning. There the gas is liquefied in the condenser, where the heat of vaporization is released, and evaporated in the evaporator, where the heat of vaporization is absorbed. Ammonia was the 1 first such refrigerant, and is still in widespread use in industrial refrigeration, but it has largely been replaced by compounds derived from petroleum and halogens in residential and commercial applications. Liquid oxygen is provided to hospitals for conversion to gas for patients with breathing problems, and liquid nitrogen is used in the medical field for cryosurgery, and by inseminators to freeze semen. Liquefied chlorine is transported for eventual solution in water, after which it is used for water purification, sanitation of industrial waste, sewage and swimming pools, bleaching of pulp and textiles and manufacture of carbon tetrachloride, glycol and numerous other organic compounds as well as phosgene gas. Liquefaction of helium (4He) with the Hampson-Linde cycle led to a Nobel Prize for Heike Kamerlingh Onnes in 1913. At ambient pressure the boiling point of liquefied helium is 4.22 K (-268.93°C). Below 2.17 K liquid 4He becomes a superfluid (Nobel Prize 1978, Pyotr Kapitsa) and shows characteristic properties such as heat conduction through second sound, zero viscosity and the fountain effect among others. The liquefaction of gases is a complicated process that uses various compressions and expansions to achieve high pressures and very low temperatures, using, for example,turboexpanders. The liquefaction of air is used to obtain nitrogen, oxygen, and argon and other atmospheric noble gases by separating the air components by fractional distillation in an cryogenic air separation unit. History Further information: Timeline of low-temperature technology Linde's Process Air is liquefied by the Linde process, in which air is alternately compressed, cooled, and expanded, the expansion resulting each time in a considerable reduction in temperature. With the lower temperature the molecules move more slowly and occupy less space, so the air changes phase to become liquid ,this makes it to lose heat and become a liquid Claude's Process Air can also be liquefied by Claude's process in which the gas is allowed to expand isentropically twice in two chambers. While expanding, the gas has to 2 do work as it is led through an expansion turbine. The gas is not yet liquefied, since it would destroy the turbine. Final liquefaction takes place by isenthalpic expansion in a Joule-Thomson-Valve. Supercritical drying From Wikipedia, the free encyclopedia Supercritical drying (red arrow) goes beyond the critical point of the working fluid in order to avoid the direct liquid–gas transition seen in ordinary drying (green arrow) or the two phase changes in freeze-drying (blue arrow). Supercritical drying is a process to remove liquid in a precise and controlled way. It is useful in the production of microelectromechanical systems (MEMS), the drying of spices, the production of aerogel, the decaffeination of coffee and in the preparation of biological specimens for scanning electron microscopy. As the substance in a liquid body crosses the boundary from liquid to gas (see green arrow in phase diagram), the liquid changes into gas at a finite rate, while the amount of liquid decreases. When this happens within a heterogeneous environment, surface tension in the liquid body pulls against any solid structures the liquid might be in contact with. Delicate structures such as cell walls, the dendrites in silica gel, and the tiny machinery of microelectromechanical devices, tend to be broken apart by this surface tension as the liquid–gas–solid junction moves by. To avoid this, the sample can be brought via two possible alternate paths from the liquid phase to the gas phase without crossing the liquid–gas boundary on the phase diagram. In freeze-drying, this means going around to the left (low temperature, low pressure; blue arrow). However, some structures are disrupted even by the solid–gas boundary. Supercritical drying, on the other hand, goes around the line to the right, on the high-temperature, high-pressure side (red arrow). This route from liquid to gas does not cross any phase boundary, instead 3 passing through the supercritical region, where the distinction between gas and liquid ceases to apply. Densities of the liquid phase and vapor phase become equal at critical point of drying. Phase diagram showing the supercritical region (light blue) ofcarbon dioxide. Fluids suitable for supercritical drying include carbon dioxide (critical point 304.25 K at 7.39 MPa or 31.1 °C at 1072 psi) and freon (≈300 K at 3.5–4 MPa or 25–0 °C at 500–600 psi). Nitrous oxide has similar physical behavior to carbon dioxide, but is a powerful oxidizer in its supercritical state. Supercritical water is inconvenient due to possible heat damage to a sample at its critical point temperature (647 K, 374 °C)[1] and corrosiveness of water at such high temperatures and pressures (22.064 MPa, 3,212 psi). In most such processes, acetone is first used to wash away all water, exploiting the complete miscibility of these two fluids. The acetone is then washed away with high pressure liquid carbon dioxide, the industry standard now that freon is unavailable. The liquid carbon dioxide is then heated until its temperature goes beyond the critical point, at which time the pressure can be gradually released, allowing the gas to escape and leaving a dried product. perishable material or make the material more convenient for transport. Freeze- drying works by freezing the material and then reducing the surrounding pressure to allow the frozen water in the material to sublimate directly from the solid phase to the gas phase. The origins of freeze drying[ The Andean civilizations preserved potatoes using a freeze drying process. They called this foodstuff chuño.[1] Modern freeze-drying was developed during WWII. Serum being sent to Europe from the US for medical treatment of the wounded required refrigeration, but because of the lack of simultaneous refrigeration and transport, many serum 4 supplies were spoiling before reaching their intended recipients. The freeze- drying process was developed as a commercial technique that enabled serum to be rendered chemically stable and viable without having to be refrigerated. Shortly thereafter, the freeze-dry process was applied to penicillin and bone, and lyophilization became recognized as an important technique for preservation of biologicals. Since that time, freeze-drying has been used as a preservation or processing technique for a wide variety of products. These applications include the following but are not limited to: the processing of food,[2] pharmaceuticals,[3] and diagnostic kits; the restoration of water damaged documents;[4] the preparation of river-bottom sludge for hydrocarbon analysis; the manufacturing of ceramics used in the semiconductor industry; the production of synthetic skin; the manufacture of sulphur-coated vials; and the restoration of historic/reclaimed boat hulls. The freeze-drying stages[ There are four stages in the complete drying process: pretreatment, freezing, primary drying, and secondary drying. Pretreatment[ Pretreatment includes any method of treating the product prior to freezing. This may include concentrating the product, formulation revision (i.e., addition of components to increase stability and/or improve processing), decreasing a high vapor pressure solvent or increasing the surface area. In many instances the decision to pretreat a product is based on theoretical knowledge of freeze- drying and its requirements, or is demanded by cycle time or product quality considerations. Methods of pretreatment include: freeze concentration, solution phase concentration, formulation to preserve product appearance, formulation to stabilize reactive products, formulation to increase the surface area, and decreasing high vapor pressure solvents.[5] Freezing[ In a lab, this is often done by placing the material in a freeze-drying flask and rotating the flask in a bath, called a shell freezer, which is cooled by mechanical refrigeration, dry iceand methanol, or liquid nitrogen. On a larger scale, freezing is usually done using a freeze-drying machine. In this step, it is important to cool the material below its triple point, the lowest temperature at which the solid and liquid phases of the material can coexist. This ensures that sublimation rather than melting will occur in the following steps. Larger crystals are easier to freeze- dry. To produce larger crystals, the product should be frozen slowly or can be 5 cycled up and down in temperature. This cycling process is called annealing. However, in the case of food, or objects with formerly-living cells, large ice crystals will break the cell walls (a problem discovered, and solved, by Clarence Birdseye), resulting in the destruction of more cells, which can result in increasingly poor texture and nutritive content. In this case, the freezing is done rapidly, in order to lower the material to below itseutectic point quickly, thus avoiding the formation of ice crystals.
Load more

Recommended publications
  • Supercritical Gel Drying of Polymeric Hydrogels for Tissue
    1123 A publication of CHEMICAL ENGINEERING TRANSACTIONS The Italian Association VOL. 32, 2013 of Chemical Engineering Online at: www.aidic.it/cet Chief Editors: Sauro Pierucci, Jiří J. Klemeš Copyright © 2013, AIDIC Servizi S.r.l., ISBN 978-88-95608-23-5; ISSN 1974-9791 Supercritical Gel Drying of Polymeric Hydrogels for Tissue Engineering Applications Stefano Cardea*, Lucia Baldino, Iolanda De Marco, Paola Pisanti, Ernesto Reverchon Department of Industrial Engineering, University of Salerno, Via Ponte Don Melillo, 84084, Fisciano, Italy [email protected] Tissue engineering (TE) is an emerging field aimed at repairing defective tissues and organ, instead of relying on conventional organ transplantation. Among the polymeric materials proposed for TE applications, the water-soluble polymers have been frequently used in form of hydrogels, that are a class of highly hydrated polymer materials. Nevertheless, hydrogel materials have poor mechanical properties; as a result, this scaffolding approach is seldom used for hard tissues applications. With the aim of overcoming this limitation, drying processes have been often applied to eliminate the water from hydrogels and amply the range of applications of the water-soluble polymeric scaffolds, but these techniques present several limitations. For this reason, in this work we proposed a supercritical gel drying method coupled with a water/solvent substitution step. PVA, Alginate and Chitosan hydrogels were processed and opportunely characterized from a macroscopic and microscopic point of view. Supercritical gel drying process confirmed to be effectiveness for the formation of polymeric scaffolds; in particular, we obtained stable 3-D structures with nanometric porous morphologies suitable for TE applications. 1. Introduction Tissue engineering (TE) is an emerging field aimed at repairing defective tissues and organ, instead of relying on conventional organ transplantation.
    [Show full text]
  • The Role of Supercritical CO2 in the Drying of Porous Silicon
    Rev. Energ. Ren.: ICPWE (2003) 99-102 The Role of Supercritical CO2 in the Drying of Porous Silicon M. Bouchaour, N. Diaf, A. Ould-Abbas, M. Benosman, L. Merad and N-E. Chabane-Sari Laboratoire de Matériaux & Energies Renouvelables (LMER), Faculté des Sciences, Université Abou Bekr Belkaïd, B. P 119, Tlemcen,13000, Algérie. E-mail : [email protected] Abstract – The study of light emission from porous silicon has attracted great interest since the first observation of its photoluminescence at room temperature [1]. Recently, particular interest is devoted to supercritical fluid CO2 [2] applications on the drying of this semiconductor. This fluid is inotoxic, non- flammable, unreactive under most conditions, leaves no liquid waste. It has a potential to ameliorate environmental safety and health impact and it enables innovative processing technologies and material protection [3]. This talk reviews the mechanism of supercritical drying of porous silicon and the role of this fluid in this process. Résumé – L'étude de l'émission de la lumière du silicium poreux a attiré un grand intérêt depuis la première observation de la photoluminescence à la température ambiante [1]. Récemment, l'intérêt particulier est consacré aux applications du fluide supercritique CO2 [2] sur le séchage de ce semi-conducteur. Ce fluide est non toxique, inflammable. Il offre des possibilités intéressantes d'améliorer la sûreté environnementale et est utilisé dans des nouvelles technologies afin d’assurer la protection matérielle [3]. Ce papier concerne le mécanisme du séchage supercritique du silicium poreux et le rôle du fluide supercritique CO2 dans ce processus. Key-Words: Porous silicon – Supercritical drying – Supercritical fluid CO2.
    [Show full text]
  • Application of Supercritical Fluids Review Yoshiaki Fukushima
    1 Application of Supercritical Fluids Review Yoshiaki Fukushima Abstract Many advantages of supercritical fluids come Supercritical water is expected to be useful in from their interesting or unusual properties which waste treatment. Although they show high liquid solvents and gas carriers do not possess. solubility solutes and molecular catalyses, solvent Such properties and possible applications of molecules under supercritical conditions gently supercritical fluids are reviewed. As these fluids solvate solute molecules and have little influence never condense at above their critical on the activities of the solutes and catalysts. This temperatures, supercritical drying is useful to property would be attributed to the local density prepare dry-gel. The solubility and other fluctuations around each molecule due to high important parameters as a solvent can be adjusted molecular mobility. The fluctuations in the continuously. Supercritical fluids show supercritical fluids would produce heterogeneity advantages as solvents for extraction, coating or that would provide novel chemical reactions with chemical reactions thanks to these properties. molecular catalyses, heterogenous solid catalyses, Supercritical water shows a high organic matter enzymes or solid adsorbents. solubility and a strong hydrolyzing ability. Supercritical fluid, Supercritical water, Solubility, Solvation, Waste treatment, Keywords Coating, Organic reaction applications development reached the initial peak 1. Introduction during the period from the second half of the 1960s There has been rising concern in recent years over to the 1970s followed by the secondary peak about supercritical fluids for organic waste treatment and 15 years later. The initial peak was for the other applications. The discovery of the presence of separation and extraction technique as represented 1) critical point dates back to 1822.
    [Show full text]
  • Using Supercritical Fluid Technology As a Green Alternative During the Preparation of Drug Delivery Systems
    pharmaceutics Review Using Supercritical Fluid Technology as a Green Alternative During the Preparation of Drug Delivery Systems Paroma Chakravarty 1, Amin Famili 2, Karthik Nagapudi 1 and Mohammad A. Al-Sayah 2,* 1 Small Molecule Pharmaceutics, Genentech, Inc. So. San Francisco, CA 94080, USA; [email protected] (P.C.); [email protected] (K.N.) 2 Small Molecule Analytical Chemistry, Genentech, Inc. So. San Francisco, CA 94080, USA; [email protected] * Correspondence: [email protected]; Tel.: +650-467-3810 Received: 3 October 2019; Accepted: 18 November 2019; Published: 25 November 2019 Abstract: Micro- and nano-carrier formulations have been developed as drug delivery systems for active pharmaceutical ingredients (APIs) that suffer from poor physico-chemical, pharmacokinetic, and pharmacodynamic properties. Encapsulating the APIs in such systems can help improve their stability by protecting them from harsh conditions such as light, oxygen, temperature, pH, enzymes, and others. Consequently, the API’s dissolution rate and bioavailability are tremendously improved. Conventional techniques used in the production of these drug carrier formulations have several drawbacks, including thermal and chemical stability of the APIs, excessive use of organic solvents, high residual solvent levels, difficult particle size control and distributions, drug loading-related challenges, and time and energy consumption. This review illustrates how supercritical fluid (SCF) technologies can be superior in controlling the morphology of API particles and in the production of drug carriers due to SCF’s non-toxic, inert, economical, and environmentally friendly properties. The SCF’s advantages, benefits, and various preparation methods are discussed. Drug carrier formulations discussed in this review include microparticles, nanoparticles, polymeric membranes, aerogels, microporous foams, solid lipid nanoparticles, and liposomes.
    [Show full text]
  • OP03 Contribution of Computational Fluid Dynamics And
    OP03 Contribution of Computational Fluid Dynamics and Thermodynamics to the development of supercritical carbon dioxide extraction processes Renan RAVETTI DURAN, Mouna LAZRAG, Romain PRIVAT, Cécile LEMAITRE, Danielle BARTH* Laboratoire Réactions et Génie des Procédés, UMR CNRS 7274, Université de Lorraine 1 rue Grandville-BP20451-54001 NANCY-France * [email protected] ABSTRACT In supercritical CO2 extraction process , there are two essential steps: the extraction step in the extractor where the SC-CO2 allows the solvent or extract removal from product structure and the separation step which consists of the separation of CO2-solvents or CO2-extract in a cascade of cyclone separators downstream the extractor. Cyclone separators are separation devices that use the centrifugal and gravity forces to remove liquid phase from flue gases. Two supercritical extraction processes are studied here: organogels supercritical drying for aerogels production and supercritical extraction of polar compounds from natural products. Concerning the first process, the organogel is prepared by an aminoacid-type organogelator with aromatic solvents such as tetralin or toluene. The experimental results showed a good solvent recovery rate in the case of tetralin, exceeding 90% but an unsatisfactory separation for toluene with a yield below 65%. In order to understand the experimental results a thermodynamic study and a hydrodynamic study (CFD) of the mixture separation in the cyclones are carried out. Supercritical extraction of polar compounds from natural products using a CO2 + aqueous ethanol mixture as solvent requires a reliable knowledge of vapor-liquid equilibria of the carbon dioxide + ethanol + water system in order to size and optimize the extraction process.
    [Show full text]
  • SUPERCRITICAL FLUID SPRAY APPLICATION PROCESS for ADHESIVES and PRIMERS SERDP Project PP-1118 Marc D. Donohue Principal Investi
    SUPERCRITICAL FLUID SPRAY APPLICATION PROCESS FOR ADHESIVES AND PRIMERS SERDP Project PP-1118 Marc D. Donohue Principal Investigator Johns Hopkins University March 2003 Preface Project Background In this project, we reformulated various solvent borne, high volatile organic compound (VOC) adhesives and adhesive primers, as cited in SERDP’s Statement of Need, for application by a supercritical carbon dioxide spray process. Over the last several years, a new spray application process has been developed for polymeric based paints and other coatings that can reduce solvent VOC emissions up to 80%. This process was conceived by the principal investigator of this project and has been commercialized by the Dow Chemical Company. This unique process (known as the UNICARBâ process) is based on the use of supercritical carbon dioxide as a replacement for organic solvents in multi-component spray coating formulations. By adapting this process to adhesives and adhesive primer applications, stringent compliance standards can be achieved respective to environmental, toxicological, materials compatibility, and, physical property performance characteristics as outlined in the original proposal and Statement of Need. Furthermore, by employing this process to apply adhesives that are presently used in the military, the costs incurred for developing and testing new (different) low/no-VOC, non-structural adhesives will be negated. To accomplish this task, a systematic program was implemented aimed at understanding the thermodynamic and rheological properties of adhesive-solvent-carbon dioxide mixtures for each type of adhesive and primer. Additionally, optimal conditions of temperature, pressure, and polymer/solvent ratio were determined for each adhesive and primer type such that proper atomization and film formation was achieved while simultaneously VOC emissions are minimized.
    [Show full text]
  • Synthesis of Organic Aerogels with Tailorable Morphology and Strength
    www.nature.com/scientificreports OPEN Synthesis of organic aerogels with tailorable morphology and strength by controlled solvent swelling Received: 18 October 2017 Accepted: 18 December 2017 following Hansen solubility Published: xx xx xxxx Anurodh Tripathi 1, Gregory N. Parsons 1, Saad A. Khan1 & Orlando J. Rojas 1,2 We introduce a generalized approach to synthesize aerogels that allows remarkable control over its mechanical properties. The Hansen solubility parameters are used to predict and regulate the swelling properties of the precursor gels and, consequently, to achieve aerogels with tailored density and mechanical properties. As a demonstration, crosslinked organogels were synthesized from cellulose esters to generate aerogels. By determination of Hansen’s Relative Energy Diference, it was possible to overcome the limitations of current approaches that solely rely on the choice of precursor polymer concentration to achieve a set of aerogel properties. Hence, from a given concentration, aerogels were produced in a range of mass densities, from 25 to 113 mg/cm3. Consequently, it was possible to tailor the stifness, toughness and compressive strength of the aerogels, in the ranges between 14–340, 4–103 and 22–373 kPa, respectively. Additionally, unidirectional freeze-drying introduced pore alignment in aerogels with honeycomb morphologies and anisotropy. Interestingly, when the swelling of the polymeric gel was arrested in a non-equilibrium state, it was possible to gain additional control of the property space. The proposed method is a novel and generic solution to achieving full control of aerogel development, which up to now has been an intractable challenge. Since the introduction of aerogels in 19311, they have been synthesized from a variety of sources that include inor- ganic materials2, synthetic polymers3, biopolymers4 and carbons5; they have been recognized as promising systems for a plethora of applications, including membrane separation6, catalysis7, thermal and acoustic insulation8, fame resistance9 and sorption10.
    [Show full text]
  • Supercritical Carbon Dioxide Treatment of Natural Biomaterials for Tissue Engineering Applications Dominic M
    University of South Carolina Scholar Commons Theses and Dissertations 2017 Supercritical Carbon Dioxide Treatment Of Natural Biomaterials For Tissue Engineering Applications Dominic M. Casali University of South Carolina Follow this and additional works at: https://scholarcommons.sc.edu/etd Part of the Chemical Engineering Commons Recommended Citation Casali, D. M.(2017). Supercritical Carbon Dioxide Treatment Of Natural Biomaterials For Tissue Engineering Applications. (Doctoral dissertation). Retrieved from https://scholarcommons.sc.edu/etd/4065 This Open Access Dissertation is brought to you by Scholar Commons. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. SUPERCRITICAL CARBON DIOXIDE TREATMENT OF NATURAL BIOMATERIALS FOR TISSUE ENGINEERING APPLICATIONS by Dominic M. Casali Bachelor of Science Florida Institute of Technology, 2011 Submitted in Partial Fulfillment of the Requirements For the Degree of Doctor of Philosophy in Chemical Engineering College of Engineering and Computing University of South Carolina 2017 Accepted by: Michael A. Matthews, Major Professor Ehsan Jabbarzadeh, Committee Member Tarek Shazly, Committee Member Mark J. Uline, Committee Member John W. Weidner, Committee Member Cheryl L. Addy, Vice Provost and Dean of the Graduate School © Copyright by Dominic M. Casali, 2017 All Rights Reserved. ii Dedication To Grandpa Carmine, who could have written a great dissertation about gardening and making wine. iii Acknowledgements First and foremost, thanks be to God above, whose assistance has been needed regularly throughout the past few years. Thanks as well to my parents, Al and Ann, and my brother, Joe, for their constant and unconditional love and support, as well as Grandma Terry and my extended family in New York.
    [Show full text]
  • WO 2014/153570 A9 25 September 2014 (25.09.2014) P O P C T
    (12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) CORRECTED VERSION (19) World Intellectual Property Organization I International Bureau (10) International Publication Number (43) International Publication Date WO 2014/153570 A9 25 September 2014 (25.09.2014) P O P C T (51) International Patent Classification: (74) Agents: HERSHKOVITZ, Abraham et al; Hershkovitz CIOB 49/12 (2006.01) & Associates PLLC, 2845 Duke Street, Alexandria, VA 223 14 (US). (21) International Application Number: PCT/US20 14/038290 (81) Designated States (unless otherwise indicated, for every kind of national protection available): AE, AG, AL, AM, (22) Date: International Filing AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY, 15 May 2014 (15.05.2014) BZ, CA, CH, CL, CN, CO, CR, CU, CZ, DE, DK, DM, (25) Filing Language: English DO, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, HN, HR, HU, ID, IL, IN, IR, IS, JP, KE, KG, KN, KP, KR, (26) Publication Language: English KZ, LA, LC, LK, LR, LS, LT, LU, LY, MA, MD, ME, (30) Priority Data: MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ, 61/801,491 15 March 2013 (15.03.2013) US OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA, SC, SD, SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, TM, (71) Applicant: TRANSTAR GROUP, LTD [— /CN]; China TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, Overseas Building, Room A, 7F, 139 Hennessy Road, ZW. Wanchai, Hong Kong (CN). (84) Designated States (unless otherwise indicated, for every (72) Inventors; and kind of regional protection available): ARIPO (BW, GH, (71) Applicants : KALPAN, Allen [US/US]; Post Office Box GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, SZ, TZ, 191344, Miami Beach, FL 33 119-1344 (US).
    [Show full text]
  • Drying of Foodstuff Using Supercritical Carbon Dioxide
    THE DRYING OF FOODS USING SUPERCRITICAL CARBON DIOXIDE ZOË KATHERINE BROWN A Thesis Submitted to The University of Birmingham for the Degree of Doctor of Engineering Department of Chemical Engineering The University of Birmingham October 200 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. SUMMARY Food drying techniques such as air and freeze drying are not ideal: high temperatures used during air drying result in degradation of nutrients and sensorial properties, while freeze drying is expensive and therefore only applicable to high value foods. As an alternative to such drying techniques, drying with supercritical carbon dioxide was investigated here. Initially, carrot was dried using this technique. Addition of a co-solvent (ethanol) to the supercritical fluid was used as a method to increase the water solubility in the supercritical fluid and therefore aid drying. Analysis of the dried and rehydrated product structure, rehydration properties and mechanical properties was carried out which gave an indication of product quality. Drying of agar, containing varying concentrations of sugar was carried out on a laboratory and pilot plant scale. Gel structure and gel properties were studied.
    [Show full text]
  • Supercritical Drying of Cementitious Materials Zhidong Zhang, George Scherer
    Supercritical drying of cementitious materials Zhidong Zhang, George Scherer To cite this version: Zhidong Zhang, George Scherer. Supercritical drying of cementitious materials. Cement and Concrete Research, Elsevier, 2017, 99, pp.137-154. 10.1016/j.cemconres.2017.05.005. hal-01622913 HAL Id: hal-01622913 https://hal-enpc.archives-ouvertes.fr/hal-01622913 Submitted on 24 Oct 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Supercritical drying of cementitious materials Zhidong Zhang, George W. Scherer∗ aDepartment of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544, USA Abstract Techniques to characterize the microstructure of hydrated cement require dried materials. However, the microstructure of hydrated products is significantly altered by high capillary forces during drying when using the conventional drying methods. To avoid drying stresses when preparing samples, we have employed supercritical drying (SCD) which has been used for decades to prepare aerogels that undergo no shrinkage during drying, but has rarely been used for cementitious materials. The pore solution is first replaced with isopropanol, and then with trifluoromethane (R23). The temperature and pressure are raised above the critical point, where no menisci or capillary pressure can exist; therefore, the dried samples are free of artifacts created by stresses.
    [Show full text]
  • Supercritical Drying for Water-Rinsed Resist Systems
    Supercritical drying for water-rinsed resist systems Hideo Namatsua) NTT Basic Research Laboratories, 3-1 Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198, Japan ͑Received 1 June 2000; accepted 1 August 2000͒ ͑ ͒ Two methods of supercritical resist drying SRD using CO2 have been developed for water-rinsed resist patterns. The key to their effectiveness is the use of a surfactant. In indirect SRD, a solution of n-hexane, a CO2-philic liquid, and a surfactant, sorbitan fatty acid ether, first replaces the water, and is in turn replaced with liquid CO2 before SRD is performed. The addition of a compound with a high hydrophilic-lipophilic balance to the surfactant compensates for the poor miscibility of water in a solution of n-hexane and sorbitan fatty acid ether. In direct SRD, which does not require a CO2-philic liquid, the water is replaced directly with liquid CO2 containing a surfactant, fluoroether carboxylate, which makes water miscible in CO2 ; and then SRD is performed. The excellent results obtained by both methods demonstrate that there is no inherent barrier to the use of SRD on water-rinsed resist patterns. © 2000 American Vacuum Society. ͓S0734-211X͑00͒01406-2͔ I. INTRODUCTION Thus, we have found that good results can be obtained by drying resist patterns rinsed with alcohol in supercritical To fabricate nanodevices with dimensions less than 100 CO2, provided that water contamination is prevented. How- nm, we need fabrication techniques with increased resolution ever, for some resist systems, water itself is used for rinsing, capabilities. However, increased resolution results in the for- for example, after development in an alkaline solution such mation of patterns with a high aspect ratio, which is the ratio as an aqueous solution of tetramethyl ammonium hydroxide of line height to linewidth.
    [Show full text]